Power module

Abstract

A power module is disclosed, including a power module substrate in which a circuit layer is arranged on one surface of an insulating layer; and a semiconductor element that is bonded onto the circuit layer, in which a copper layer composed of copper or a copper alloy is provided on a surface of the circuit layer to be bonded to the semiconductor element, a solder layer formed by using a solder material between the circuit layer and the semiconductor element is provided, an alloy layer containing Sn as a main component, 0.5% by mass or more and 10% by mass or less of Ni, and 30% by mass or more and 40% by mass or less of Cu at an interface of the solder layer with the circuit layer is formed, and the coverage of the alloy layer at the interface is 85% or more.

The invention claimed is: 
     
       1. A power module, comprising:
 a power module substrate in which a circuit layer is arranged on one surface of an insulating layer; and 
 a semiconductor element that is bonded onto the circuit layer, 
 wherein a copper layer composed of copper or a copper alloy is provided on a surface of the circuit layer to be bonded to the semiconductor element, 
 a solder layer composed of a solder material between the circuit layer and the semiconductor element is provided, 
 an alloy layer containing Sn as a main component, 0.5% by mass or more and 10% by mass or less of Ni, and 30% by mass or more and 40% by mass or less of Cu at an interface of the solder layer with the circuit layer is formed, 
 the coverage of the alloy layer at the interface is 85% or more and 96% or less, 
 the interface between the solder layer and the circuit layer is free of a Ni plating film, 
 the coverage of the alloy layer at the interface is the average value of a ratio (LC/L) calculated for each cross-section observation, by performing a plurality of times of cross-sectional observation of the solder layer and the circuit layer by an electron microscope, and 
 the ratio (LC/L) is a ratio of the length LC of the interface covered by the alloy layer to the total length L of the interfaces observed in each cross-section observation. 
 
     
     
       2. The power module according to  claim 1 ,
 wherein a thermal resistance increase rate when a power cycle is loaded 100,000 times under conditions of a conduction duration of 5 seconds and a temperature difference of 80° C. is less than 10% in a power cycle test. 
 
     
     
       3. The power module according to  claim 2 ,
 wherein a thickness of the alloy layer is within a range of 2 μm or more and 20 μm or less. 
 
     
     
       4. The power module according to  claim 3 ,
 wherein the alloy layer includes an intermetallic compound composed of (Cu, Ni) 6 Sn 5 . 
 
     
     
       5. The power module according to  claim 2 ,
 wherein the alloy layer includes an intermetallic compound composed of (Cu, Ni) 6 Sn 5 . 
 
     
     
       6. The power module according to  claim 1 ,
 wherein a thickness of the alloy layer is within a range of 2 μm or more and 20 μm or less. 
 
     
     
       7. The power module according to  claim 6 ,
 wherein the alloy layer includes an intermetallic compound composed of (Cu, Ni) 6 Sn 5 . 
 
     
     
       8. The power module according to  claim 1 ,
 wherein the alloy layer includes an intermetallic compound composed of (Cu, Ni) 6 Sn 5 . 
 
     
     
       9. The power module according to  claim 8 , further comprising,
 an intermetallic compound layer composed of Cu 3 Sn and provided between the alloy layer and the circuit layer is provided. 
 
     
     
       10. The power module according to  claim 9 ,
 wherein the intermetallic compound layer is not formed in a region where the alloy layer is not formed. 
 
     
     
       11. The power module according to  claim 9 ,
 wherein the intermetallic compound layer is thinner than the alloy layer. 
 
     
     
       12. The power module according to  claim 10 ,
 wherein the intermetallic compound layer is thinner than the alloy layer. 
 
     
     
       13. The power module according to  claim 1 , further comprising,
 an intermetallic compound layer composed of Cu 3 Sn and provided between the alloy layer and the circuit layer is provided. 
 
     
     
       14. The power module according to  claim 13 ,
 wherein the intermetallic compound layer is not formed in a region where the alloy layer is not formed. 
 
     
     
       15. The power module according to  claim 13 ,
 wherein the intermetallic compound layer is thinner than the alloy layer. 
 
     
     
       16. The power module according to  claim 14 ,
 wherein the intermetallic compound layer is thinner than the alloy layer. 
 
     
     
       17. The power module according to  claim 1 ,
 wherein a thickness of the copper layer is within a range of 5 μm or more and 3 mm or less.